CEE 321 Structural Analysis And Design Design Project 1 Feedback 1

Summary of Acceptable Designs Total Cost ($) Economy of Design Score Total Score Comments 649, Sizing. Bracing, asymmetric design. 654, Sizing. Bracing. 691, Sizing 2

Common Modeling Errors Not using consistent units – Mass density should be in slugs not pounds Live loads – Live load reductions cannot be taken for floor loadings. See Blackboard Discussion thread. – Roof live load – incorrect computation of tributary area 3

Common Modeling Errors Incorrect design model – Used Y-Disp instead of X-Disp – Incorrect cost computation for joints – No stress constraints imposed – Acceleration value is incorrect – Final model did not have all the load cases – Invalid relationship between x/s dimensions 4

Common Modeling Errors Need to consider wind loads parallel and normal to ridge (at a minimum for the final checks) All floor live loads are the same 5

Common Hand Calc. Errors Hand calculations – Use governing load cases and other load cases randomly selected – FBDs of joints and members – Euler Buckling check (compressive member and safety factor) – Euler Buckling load (P cr ) is in lb NOT psi – Stress check 6

Report Writing Summarizing the problem statement Using correct tense in the report Words such as “us”, ”we” and “our” should not be used in technical report Round off the numbers to significant digits Summary tables of the total hours each student performed in the group 7

Report Writing Load calculations should be discussed before describing initial design Design iteration details (design variables, total cost) Clearly state what governs the design Summarize results in the form of tables and figures 8

Design Project #2 9

GS-USA Model Use consistent units This is a frame not a truss Supports are fixed Connections are rigid 10

GS-USA Model Use command file option Shape optimization: Use the “parameter” option 11

Design Evolution Start with a simple baseline model Include all load combinations Run the design with the least number of design variables Obtain a feasible design and compute the cost (this is the upper bound on cost) Start improving – more sizing variables, shape variables, topology variables 12

Reducing Design Time See Blackboard Announcements section for reducing GS-USA time. Start with GA. Obtain a feasible solution with the fewest possible iterations. Save the design. Switch to MFD. 13

Final Design Check whether design is feasible Identify the governing load cases Hand Calculations – Overall equilibrium check – Nodal and member Equilibrium check – Element stress check – Euler Buckling check (safety factor?) 14

Report Describe the Final Design, with details : – Building layout type – Frame cost + connection cost + product cost + space usage cost – Total cost for the entire building 15

What to submit ? Submit the LOCKED GS-USA file that is reflected in the write up. Report should include – Load Calculations – Summary of initial, intermediate and final designs – GS-USA output for initial and final designs – Hand calculations for initial and final designs. 16

Questions? 17